Protein kinases (PKs) play important roles in cellular signal pathways that regulate various cell functions such as differentiation, proliferation, migration, and apoptosis. Abnormal PK activity has been linked to and observed in a number of diseases including cancer. See K. Novak, MedGenMed. 2004; 6(2): 25. Thus, protein kinases are attractive therapeutic targets. PK inhibitors, compounds that block the activities of PKs, have been developed and used widely for clinical applications. For instance, tyrosine kinase inhibitors are useful in inhibiting T-cell proliferation and thus can be utilized as immunosuppressive agents for the prevention or treatment of graft rejection following transplant surgery and also for the prevention or treatment of autoimmune diseases (e.g., rheumatoid arthritis, psoriasis, and HIV-AIDS).
While more than thirty PK inhibitors are currently under clinical trial for cancer treatment, there is still a need for developing new PK inhibitors to treat various disorders.